Biosynthesis

In mammals, fatty acids are synthesized in adipose and liver cells from glucose via a fairly complex pathway. In essence, the six carbons of a glucose molecule are oxidized to a pair of two-carbon carboxylic acid fragments called acetate. The starting point for biosynthesis is an acetate group chemically linked to a molecule of CoA (coenzyme A). The process of building up the acyl chain of a fatty acid then begins, basically through the sequential chemical addition of two-carbon fragments from CoA-acetate to generate, for example, the 16-carbon saturated fatty acid palmitate. This process is catalyzed by a complex enzyme known as fatty acid synthase. Elongation of the palmitate carbon chain and the introduction of carbon-carbon double bonds are carried out subsequently by other enzyme systems. The overall process is basically the same in organisms ranging from bacteria to humans.